Add OpenRISC support

This patch adds support for the OpenRISC architecture.
(http://opencores.org/or1k/Main_Page)

This patch has been tested under Linux with QEMU-user emulation support.
- 32 Bit
- big endian
- delayed instructions
This is the only available configuration under Linux.

The description of the ABI can be found on the official website.

Is passes the testsuite except of the unwindtest_ffi_call.cc
testcase, which seems to be a problem of gcc and not libffi.
Some testcases of the gcc testsuite still fail.

Signed-off-by: Sebastian Macke <sebastian@macke.de>

README

diff --git a/README b/README
index 765e8d7..44c070a 100644
--- a/README
+++ b/README
@@ -74,6 +74,7 @@
 | MIPS64          | Linux            | GCC                     |
 | Moxie           | Bare metal       | GCC                     |
 | Nios II         | Linux            | GCC                     |
+| OpenRISC        | Linux            | GCC                     |
 | PowerPC 32-bit  | AIX              | IBM XL C                |
 | PowerPC 64-bit  | AIX              | IBM XL C                |
 | PowerPC         | AMIGA            | GCC                     |